This application is related to Japanese Patent Applications Nos. 2000-66540, 2000-148006 and 2000-200649, filed on Mar. 10, 2000, May 19, 2000 and Jul. 3, 2000 whose priorities are claimed under 35 USC xc2xa7119, the disclosures of which are incorporated by reference in their entirety.
1. Field of the Invention
The present invention relates to an image forming apparatus such as a copier, a facsimile machine, a printer or the like which forms images on paper fed from a paper feed section by its image forming section, more particularly, an image forming apparatus which is adapted to form images continuously on a plurality of sheets of paper in a multiple state in which the sheets are partially overlapped with each other.
2. Description of Related Art
Image forming apparatus such copiers, printers and the like are strongly desired to form images in a shorter time. For this purpose, in some conventional image forming apparatus, as disclosed by Japanese Unexamined Patent Publication Nos. HEI 9(1997)-314993 and HEI 11(1999)-202683, when images are formed continuously on a plurality of sheets of paper, the sheets are transported at shortened intervals, and thereby is shortened a time necessary for the sheets from the leading end of the first sheet to the tail end of the last sheet to pass through an image forming section. Thus, a time required for an image forming operation is reduced without increasing an image forming speed. An increase in the image forming speed causes deterioration in the state of formed images.
Particularly, in constructions disclosed by Japanese Unexamined Patent Publication Nos. HEI 5(1993)-294496 and SHO 62(1987)-62373, a plurality of sheets of paper are transported to an image forming section with being overlapped with each other by a predetermined length, and thereby a time necessary for the sheets to pass through the image forming section is further shortened.
However, in the constructions disclosed by Japanese Unexamined Patent Publication Nos. HEI 5(1993)-294496 and SHO 62(1987)-62373, the length by which the sheets are overlapped with each other in a paper transport direction is not clearly specified. If this length is constant, the sheets can be overlapped only within a range of so-called voids of the sheets where images are never formed, for avoiding possible failure in image formation on the overlapped sheets, because images to be formed on the sheets have different lengths in the paper transport direction. Therefore, there is a problem that the time necessary for a plurality of sheets to pass through the image forming section cannot be shortened sufficiently.
Also, in an image forming apparatus which forms images on an electrophotographic system, sheets of paper having images of a developer transferred thereon need to be heated and pressurized at a fixing section. If two sheets partially overlapped with each other are passed through the fixing section, the two sheets adhere to each other and cannot be sent out of the apparatus smoothly.
An object of the present invention is to provide an image forming apparatus which allows the time for the image forming operation to be shortened by deleting blanks in a paper transport direction from data of images to be formed continuously, overlapping sheets of paper positioned ahead and behind in the paper transport direction by overlap amounts according to the length of the deleted blanks and reducing the time for the sheets to pass through an image forming unit to a minimum according to the length of the images to be formed on the sheets. The image forming apparatus can also separate the sheets from each other before the sheets reach a fixing section to prevent the sheets from adhering.
The present invention provides an image forming apparatus comprising: an image forming unit; a paper transport unit; and a control unit for supplying the image forming unit with image data for a plurality of pages so that the image forming unit forms images page by page on sheets transported by the paper transport unit, wherein, when the image data for each page includes data representative of blanks on a leading end side and on a tail end side of the page in a paper transport direction, the control unit deletes the data representative of the blank either on the leading end side or on the tail end side from the image data prior to supplying the image forming unit with the image data, and controls the paper transport unit so that a plurality of sheets are transported sequentially to the image formation unit in a multiple state in which one sheet partially overlaps with another in the paper transport direction by a length corresponding to the deleted data representative of the blank.
These and other objects of the present application will become more readily apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.